That maybe true, and some programs may focus a lot of USMLE score. I come from an ivy league med school, and our match average for ENT (known for the highest step 1 average) was 238 into top programs in the nation. So it makes sense that ortho is slightly lower, but ortho also has heavy emphasis on AOA and research.
Having said that, I know a lot of lower tier med school focus their first 2 year curriculum on acing step 1 whereas school like Harvard and mine have switched over to problem based learning which doesn't prepare you for step 1 at all. Although I do know 5-6 people from our school who got 260+ studying for about 2 weeks for step 1 (crazy!). Anyways, I think that maybe reason why Harvard med has only slightly above average step 1 despite having some of the top medical students in the nation (FYI I don't goto Harvard). Two top med school with reputation of still being malignant are Columbia and Johns Hopkins. Other top schools, have removed the emphasis on grades and ranking in first two years (P/F system, no preparation for step 1), which might actually be hurting us because the students coming out of lower tier schools kick a$$ in step 1.
Interesting eh? Strange how world works.